I have two MVVS engines, a 40 and a 45, they both have short pipes and really scream when propped right. The 45 is on a -4 lb. Morris Knife with a 12 1/4X 3 3/4 APC. Verticle is rather good, like forever......The 40 is looking for a new home as it lost the last one (too large for the application).
These are quality engines that put out lots of power, The 40 would most likley do well on your twist, the 45 better and the 49 great (I like the power).